(test): ensure Babel presets are merged and applied

- regression test as there was previously a bug where only plugins
  were merged and presets would only be merged if your preset list
  included preset-env
  - this is the first test that adds any sort of preset

- couldn't find a small preset that would be easy to test against, so
  made a tiny one locally that just does a simple replace with
  babel-plugin-replace-identifiers

package.json

@@ -113,6 +113,7 @@
     "@types/semver": "^7.1.0",
     "@types/styled-components": "^5.0.1",
     "autoprefixer": "^9.7.4",
+    "babel-plugin-replace-identifiers": "^0.1.1",
     "cssnano": "^4.1.10",
     "doctoc": "^1.4.0",
     "husky": "^4.2.2",

test/integration/fixtures/build-withBabel/.babelrc.js

@@ -1,4 +1,8 @@
 module.exports = {
+  presets: [
+    // ensure Babel presets are merged and applied
+    './test-babel-preset'
+  ],
   plugins: [
     'styled-components',
    ['@babel/plugin-transform-runtime', { helpers: false }],

test/integration/fixtures/build-withBabel/test-babel-preset.js

@@ -0,0 +1,4 @@
+// a simple babel preset to ensure presets are merged and applied
+module.exports = () => ({
+  plugins: [['replace-identifiers', { sum: 'replacedSum' }]],
+});

test/integration/tsdx-build-withBabel.test.js

@@ -44,6 +44,15 @@ describe('integration :: tsdx build :: .babelrc.js', () => {
     expect(matched).toBeTruthy();
   });
 
+  it('should merge and apply presets', () => {
+    const output = execWithCache('node ../dist/index.js build');
+    expect(output.code).toBe(0);
+
+    // ensures replace-identifiers was used
+    const matched = grep(/replacedSum/, ['dist/build-withbabel.*.js']);
+    expect(matched).toBeTruthy();
+  });
+
   it('should compile files into a dist directory', () => {
     const output = execWithCache('node ../dist/index.js build');
 

yarn.lock

@@ -1838,6 +1838,11 @@ babel-plugin-macros@^2.6.1:
     cosmiconfig "^6.0.0"
     resolve "^1.12.0"
 
+babel-plugin-replace-identifiers@^0.1.1:
+  version "0.1.1"
+  resolved "https://registry.yarnpkg.com/babel-plugin-replace-identifiers/-/babel-plugin-replace-identifiers-0.1.1.tgz#38819617d814ab0e4b35cfa373e40758b359f68f"
+  integrity sha1-OIGWF9gUqw5LNc+jc+QHWLNZ9o8=
+
 "babel-plugin-styled-components@>= 1":
   version "1.10.7"
   resolved "https://registry.yarnpkg.com/babel-plugin-styled-components/-/babel-plugin-styled-components-1.10.7.tgz#3494e77914e9989b33cc2d7b3b29527a949d635c"